1. Field of Invention
The present invention relates to a direct color thermal printing method, and more particularly to a direct color thermal printing method wherein a full-color image is recorded on a thermosensitive recording medium by optical recording and thermal recording.
2. Related Art
There are globally two types of thermal printers: one type is for direct thermal recording using thermosensitive recording media and the other type is for thermal transfer recording including wax thermal transfer recording and thermal dye transfer recording. The direct thermal printers print images directly on thermosensitive recording media, so that no waste, such as a dye transfer sheet, is produced. Furthermore, the construction of the direct thermal printer is simpler and thus the running cost of the direct thermal printer is lower than that of the thermal transfer printer.
Because of these preferable features, the direct thermal printers tend to be used wider and wider. For example, most facsimile transmitters are provided with monochromatic direct thermal printers. Recently, a thermosensitive color recording medium, has been suggested, for example, in Japanese Laid-open Patent Application 61-213169, which has thermosensitive coloring layers for developing magenta, cyan and yellow colors which are laminated on one another, so that full-color images can be recorded thereon using direct thermal printers.
When recording a full-color image on this type of thermosensitive color recording medium, a thermal head thermally records a yellow frame of the image in a thermosensitive recording layer of the recording medium which is developed in a yellow color and, thereafter, the recording medium is exposed to light passing through a yellow filter so as to fix the thermosensitive recording layer which is developed in yellow. Next, a cyan frame of the image is thermally recorded in a thermosensitive recording layer which is developed in a cyan color and then fixed by being exposed to light passing through a cyan filter. Finally, a magenta frame of the image is thermally recorded in a thermosensitive recording layer, which is then fixed by being exposed to light passing though a magenta filter.
Because the above described conventional direct thermal color printing method needs six steps, that is three recording steps and three fixing steps, for each recording of a full-color image, this method is extremely time-consuming.